SERVICE MANUAL
Fig. 5 Brake Valve Applied - Loss of Air In Primary
Circuit
1
Primary Piston
2
Primary Delivery
3
Relay Piston
4
Secondary Delivery
5
Secondary Exhaust Valve Closed
6
Secondary Inlet Valve Open
7
Secondary Supply
8
No Air in Primary Circuit
Balanced - Secondary Circuit of Brake Valve (Fig. A)
When the air pressure on the secondary side of the relay
piston approaches that being delivered on the primary
side of the relay piston, the relay piston moves closing
the secondary inlet valve and stopping further flow of air
pressure from the supply line through the valve. The
exhaust remains closed as the secondary supply
pressure balances the secondary delivery pressure.
When applications in the graduating range are made, a
balanced position in the primary portion is reached as the
air pressure on the delivery side of the primary piston
equals the effort exerted by the driver’s foot on the pedal
or treadle.
A balanced position in the secondary portion is reached
when air pressure on the secondary side of the relay
piston closely approaches the air pressure on the
primary side of the relay piston .
Fig. 6 Broke Valve In Balanced Position
1
Primary Piston
2
Primary Delivery
3
Primary Exhaust Valve Closed
4
Relay Piston
5
Secondary Delivery
6
Secondary Exhaust Valve Closed
7
Secondary Inlet Valve Closed
8
Secondary Supply
9
Primary Inlet Valve Closed
10
Primary Supply
When the brake pedal or treadle is fully depressed, both
primary and secondary inlet valves remain open and full
reservoir pressure is delivered to the actuators.
Releasing - Primary Circuit of Brake Valve (Fig. 7)
With the brake pedal released, mechanical force is
removed from the spring seat, rubber graduating spring
and primary piston. Air pressure and spring load move
the primary piston, opening the primary exhaust valve,
allowing air pressure in the primary delivery line to
exhaust out the exhaust port.
Releasing - Secondary Circuit of Brake Valve (Fig. 7)
With the brake pedal released, air is exhausted from the
primary side of the relay piston. Air pressure and spring
load move the relay piston, opening the secondary
exhaust valve, allowing air pressure in the secondary
delivery line to exhaust out the exhaust port.
CTS-4079 - CHAPTER IV
PRINTED IN UNITED STATES OF AMERICA
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